As RF power amplifier designers weigh cost, efficiency, linearity, thermal performance and peak power in transistors, Phoenix, Ariz. based fabless semiconductor start-up HVVi Semiconductors, Inc., is giving engineers a new silicon alternative. Unlike LDMOS, the company has taken vertical path to far exceed the capabilities of current bipolar and LDMOS transistors. According to the developer, it has developed an unprecedented high frequency, high voltage vertical FET (HVVFET) architecture that delivers an unsurpassed frequency bandwidth, voltage and power levels to radar and avionic applications. In short, HVVi claims to have readied a revolutionary new patent-pending architecture to achieve performance levels comparable to non-silicon technologies at much more attractive cost levels.

“While currently-used silicon RF transistor technologies such as bipolar and LDMOS have served radar and avionics designers well, they have hit a ceiling in terms of performance,” said Wil Salhuana, president and CEO. “By creating the first high frequency, high voltage vertical field effect transistor, we have redefined the performance capabilities of the discrete silicon power transistor and opened the door to a vast array of new applications.”

The patent pending HVVFET is developed by a team of experts, which includes Bob Davies, the key inventor of LDMOS. The HVVFET is implemented in mature CMOS. And the company will utilize ON Semiconductor for wafer fabrication and Richardson Electronics for worldwide distribution.

Initially, the supplier is unwrapping three parts based on this innovative new HVVFET architecture. Targeted at high power, pulsed RF applications in the L-band such as IFF, TCAS, TACAN and Mode-S, the three new devices leverage the inherent benefits of the HVVFET process to deliver high output power and high gain in an extremely compact package. All three transistors are designed to operate at 48 V. Plus, the vertical structure allows the heat to be extracted from the hottest spot of the device directly to the heatsink. In a lateral structure, the heat path is about 100 µm, while the vertical design cuts that down to less than 10 µm (Figure 1). Thus, enabling more efficient thermal management for better reliability and improved MTBF.

To overcome the limitations of older vertical designs like parasitics associated with silicon substrates, the HVVi uses a novel edge termination structure and a unique gate-drain faraday shield to minimize these effects. In addition, the HVVFET’s small gate length translates into smaller capacitance and higher frequency performance. According to HVVi, the first products offer radar and avionics system designers a 30% reduction in power consumption, a 100 % increase in gain, and a tenfold increase in ruggedness.

From a system’s perspective, HVVFET’s performance advantages in terms of gain, efficiency and power density offer designers a unique opportunity to eliminate amplification stages in power amplifiers, reduce parts count, and shrink PCB space requirements, noted Brian D. Battaglia, HVVi’s senior RF applications engineer. At the same time, the technology’s higher rated ruggedness allows radar and avionics designers to eliminate bulky and costly isolators and, in the process, significantly reduce system weight, size and cost, continued Battaglia.

All the three products operate over a wide range of 24 V to 48 V supply. For pulsed applications in the L-band from 1030 to 1090 MHz, the PVV1011-300 operates at 48 V, and delivers over 300 W of pulsed output power while providing 15 dB of gain and 48% efficiency typical performance under pulsed signal conditions with a pulse width of 50 µs and a pulse period of 1 ms. The device is specified to withstand a 20:1 VSWR at all phase angles under full rated output power.

Likewise, PVV1214-25 and PVV1214-100 are enhancement mode RF transistors for L-band pulsed radar applications in the 1.2 to 1.4 GHz frequency range. Both devices operate off a 48V supply and produce 25 W and 100 W respectively. Under test conditions that generate a pulse width of 200 µS and a pulse duty cycle of 10%t, the PV1214-25 offers 17.5 dB and the PV1214-100 offers 19.5 dB of gain (typical). Both transistors are capable of withstanding an output load mismatch corresponding to a 20:1 VSWR at rated output power and nominal operating voltage across the entire frequency band of operation.

Sampling now, the HVVFETs are slated for production in the third quarter. The two high power products are in an industry standard flanged package, while the 25 W driver is housed in an innovative surface mount package (Figure 2). Evaluation kits are also available, HVVi said. Meanwhile, higher power versions going up to S band are also in the works. And are expected to be released in the fourth quarter.

www.hvvi.com

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